PDA-Presentation (Glueability+Printability+Coating+Base+Paper)

Paper Testing Technology 

PDA.C 02 

Penetration Dynamics Analyzer 

Cost and material saving 

by measurement of converting process relevant 

surface parameters of paper and board 

with an innovative measuring system 

to predict the gluability, printability and coatability 

by Dipl.-Phys. Giselher Grüner (Emtec General Manager) 

2010-11-15 

is a developer and producer of Paper Testing Technology represented worldwide by our sales-network. 

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Paper and board are usually produced for being processed further (coating, printing, 

production of corrugated board, folded boxes) respectively used by the end customer. 

Each produced paper/board is finished and/or converted further in one or the other way to 

assure the required final quality. This is done, for instance, in the coating machine, the 

printing machine or during production of corrugated board/packaging material. 

A certain specification of the paper/board is required to achieve an optimum run-ability 

during finishing or converting processes and by that an optimal result. Usually, these 

specifications are based on standard measurement methods (like Cobb test, Bendtsen 

porosimeter, Gurley porosimeter, Smoothness Beck). 

Usually all these standard specifications are complied with. However, often 

processing problems occur, but nobody knows the reasons. 

A frequently occurring problem is that standard measurement devices do not 

characterize the substantial converting relevant paper parameters. 

For solving this problem one should know what to measure for being able to predict 

processing problems reliably. For that, the process has to be analyzed and understood. 

What happens during main converting processes? 


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1. Glueing process 

Figure 1: Schematic representation of the bonding process/application of adhesive onto paper/board surfaces. 



Phase I: Pressure impulse controlled glue penetration into the paper/board surface affected by the surface pore structure and liquid rheology 

Phase II: Dewatering of the applied glue film, controlled by the surface sizing/hydrophoby ⇒ increasing of viscosity 

Phase III: Drying/fixing of the glue layer by further penetration/evaporation/hardening reaction 

Coating and printing processes are similar to the glueing process and have the same or similar demands: 

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2. Coating process 

Figure 2: Schematic representation of the coating process/application of coating color onto paper/board surfaces. 



Phase I: Pressure impulse controlled coating color penetration into the paper/board surface affected by the surface pore structure and coating 

color rheology 

Phase II: Dewatering of the applied coating color layer, controlled by the surface sizing/hydrophoby ⇒ increasing of solid content/immobilization 

Phase III: Drying of the coating layer by further penetration/evaporation 

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3. Sheet offset printing process 



Figure 3: Schematic representation of the sheet offstet printing process/application of offset ink onto paper/board surfaces. 

Phase I: Pressure impulse controlled ink/fountain solution penetration into the paper/board surface affected by the surface pore structure and 

ink rheology 

Phase II: Mineral oil/fountain solution transport from the applied ink/ink emulsion/fountain solution layer, controlled by the surface pore structure 

and partly surface sizing/hydrophoby ⇒ increasing of viscosity/fixing of the ink film, reject of fountain solution from the surface 

Phase III: Drying/final fixing of the ink layer by hardening reaction (ink oxidation) 

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• In Phase I a liquid (adhesive, coating color, printing ink/fountain solution) is applied to 

the surface of a paper/board. During that, parts of the applied liquid are pushed more 

or less deeply into the surface due to the arising extremely short (milliseconds or 

even microseconds!) pressure pulse. The penetration depth depends exclusively on 

the pressure pulse value (configuration of the application unit, machine speed), the 

surface porosity of the paper/board as well as the rheological characteristics of 

the applied liquid. 

• In Phase II, water (or oil/fountain solution from the emulsion in offset printing process) 

is transferred from the applied layer into the deeper lying surface areas of the 

paper/board (within milliseconds or seconds). This increases the viscosity within the 

liquid layer. This increase of viscosity makes sure that, after leaving the bonding 

machine, the counterparts bond immediately and the bonded parts do not come loose 

(in sheet offset process it avoids “ink set off”). This process is only dependent on 

surface sizing/hydrophoby, if water based liquids are used. 

• In Phase III (minutes or hours, in coating process seconds), the liquid dries or will be 

hardened by oxidation (sheet offset). During the bonding process this signifies the 

final fixation of the bonded parts. 

This signifies: Due to the process specifications virtually only the surface parameters 

are important for converting (gluing, printing, coating). This means especially surface 

porosity and surface hydrophoby/sizing. 


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Why does a standard porosity meter test (Bendtsen porosimeter 

ISO 5636-3, Gurley porosimeter, Mercury porosimeter) often provide not enough 

information to predict the behavior of paper/board in the converting process but sometimes 

even totally wrong information? The below schematic examples show the reason: 

Bendtsen Porosimeter test 

Bendtsen result (BS) = Bendtsen result (TS) 

Pore structure (BS) = Pore structure (TS) 

= wrong! 

Fig. 4: Schematic representation of the pore structure distribution of a paper sample in z direction 

(cross section) and the air flow from Bendtsen porosimeter test, tested both from top side and wire 

side (example) 

The air flow through the paper in z direction is controlled by the sum of the smallest pore 

diameters. 

But: because of the two-sidedness and the inhomogeneity of the paper the pore 

structure/size on one side of the paper can be totally different from the other side, or on the 

surface it can be different from the internal part! The standard methods do not show this. 

A PDA.C 02 measurement with water+Isopropylalcohol can provide information about the 

real pore structure on the surface of the paper/board: 

PDA.C 02 test 

Testing liquid: water+IPA 

contacted from BS 

t95 (BS) ≠ t95 (TS) 

= right! 

Testing liquid: water+IPA 

contacted from TS 

Fig. 5 Schematic representation of the characterization of the surface pore structure with the PDA.C 

02, using water+IPA mixture as a testing liquid 


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Why does the COBB test (ISO 535:1991(E)) often provide not enough information 

to predict the behavior of paper/board in the converting process but sometimes even totally 

wrong information? 

The below schematic examples show the reason: 

1. Sizing distribution in z-direction: sample 1 and sample 2 

high – surface sizing – low 

low – internal sizing – high 

high – surface sizing – low 

2. Water absorption speed into the two different samples (penetration depth over time) 

3. Cobb test (water penetration depth = volume over time) 

Cobb 1 ≈ Cobb 2 

= wrong! 

4. PDA testing results (time point MAX represents the surface hydrophobic/surface sizing) 

MAX (1) >> MAX (2) 

= right! 

Why you cannot get this information with the Cobb test? 

The Cobb test gives an average indication about the surface sizing plus internal sizing. 

No information about surface pore structure or/and surface sizing is possible (the same or 

even worse with HST test because of the acetic testing ink reaction with CaCO3 filler and 

long-term measurement). 


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The PDA measuring system enables measurement of process relevant parameters in the 

laboratory in an extremely easy and efficient manner, using an innovative measuring 

principle: 

Assessment of the dynamics of ultrasound transparency of paper/board, when 

contacted with appropriate testing liquids. 

Summary 

1: Measurement of the interaction between test liquid and sample surface during the first 

milliseconds (surface porosity) resp. seconds (surface hydrophoby/sizing) after contact 

Schematic representation of the evaluation time range 

Figure 6: surface porosity Figure 7: surface hydrophoby/sizing 

2: Use of appropriate test liquids to gain the desired information 

• Mixture of water+isopropyl alcohol – characterizes the effective surface porosity as 

penetration behavior of the liquid is exclusively determined by the pore structure 

• Water – characterizes the surface hydrophoby/sizing as the water penetration is 

exclusively determined by the sizing 

Figure 8: testing liquid “water+IPA” for Figure 9: testing liquid water for surface 

surface pore structure characterization hydrophoby characterization 

3. Automatic calculation of the relevant quality parameters: 

• Characterization of the surface pore structure by the time point, when the curve 

reaches 95% (or 99%) of the ultrasound transparency after the initial contact time 

point 0 (using water+IPA mixture as testing liquid) 

• Characterization of the surface sizing by the time point of the curve maximum (using 

water as testing liquid) 


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Example 


An example shall demonstrate the astonishing capabilities of the device system: 

Poor bonding characteristics of uncoated board 

Problem Description 

• The test of the bonding, realized by splitting by hand, does not result in the desired 

fiber extraction. 

Activities 

• PDA measurement of samples of good/average/poor quality with the appropriate test 

liquids (water+IPA mixture, water) 

• Evaluation of measurement outcomes 

• Identification of the reason of the problem 

• Determination of required steps 

Phase I: Adhesive application ⇒ surface pore structure 

Relevant quality parameter of paper/board: surface pore structure - measured with 

water+IPA mixture 

Figure 10: PDA diagram with testing liquid water+IPA - perfect correlation to the gluability 

In the application unit, the adhesive is applied to the board surface by a pressure 

pulse within microseconds. It depends on the surface pore structure how deep the adhesive 

is pressed into the surface during this process. Surface hydrophoby/sizing does not play any 

role in this phase. 


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Under extreme magnification, the curves measured with the PDA with water+IPA show clear 

differences between the used samples for the first 70 milliseconds. For the good-quality 

sample the curve immediately falls away sharply which points towards a very open surface 

structure. This open structure results in a good anchoring of the adhesive. For the sample of 

average quality the curve falls in a more moderate way which means that the structure of this 

sample is a little bit more closed. The poor sample with the big bonding problems differs 

extremely from the other samples. The curve has the shape of a “shoulder” which is caused 

by a very closed surface pore structure. The reason might be a too high starch concentration 

at the surface or the use of starch of poor quality in the board production process. 

Phase II: Dewatering of the applied adhesive layer in connection with an 

increase of viscosity within the layer ⇒ surface sizing 

Relevant quality parameter of paper/board: Surface sizing/hydrophoby—measured 

with water 

Figure 11: PDA diagram with testing liquid water – no correlation to the gluability 

During the milliseconds (or seconds, dependent on process speed) after leaving the 

adhesive application unit (some microseconds after application) the adhesive begins to 

dewater. This causes an increase of the viscosity of the adhesive. This results in immediate 

bonding of the added counterpart in phase III. This dewatering process is controlled by the 

surface hydrophoby of the board. The PDA determines the surface hydrophoby with water as 

testing liquid. The device analyses the first milliseconds resp. seconds after the initial water 

contact. 


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Conclusion: the prediction of gluability in this specific example is only possible with 

water+IPA mixture as a testing liquid. That means, the converting problem is caused by the 

surface pore structure. The parameter t99 gives a perfect correlation to the actual converting 

quality. The parameter MAX as a measure for the surface sizing/hydrophoby does not 

correlate with the converting properties in this example, it means, the surface sizing does not 

generate the problems. 

This example shows impressively how the PDA system can help to detect, analyze and 

predict run-ability problems and resulting quality issues. By that material, man power, time 

and money can be saved, complaints can be avoided and the converting process can be 

stabilized. 

The return on investment is extremely short for these devices, the customer satisfaction 

increases decisively and problems can be avoided before they occur. 

All emtec devices, including the wet end devices "Charge Analyzing System CAS", 

"Fiber Zeta Potential Analyzer FPA", and "Dynamic Filtration Analyzer DFA", can 

contribute to a decisive increase of efficiency of incoming control, process optimization and 

stabilization, product optimization, quality control and R&D as well as be used for efficient 

trouble shooting. They can be used in the important phases of paper and board production 

and processing from pulp, wet end, size press and coater up to the final product, before it is 

handed over to the customer for further processing or use. 

This overview shows the philosophy of the use of emtec measurement devices in the 

paper/board production process: 

Figure 12: Optimization of the paper production process using emtec devices 

� The target of any production is the end user = “the king”! 

� The final product quality will be determined by this customer. 

� The theoretical specification/demand (red lines) in each production step is 

determined by the demand of the following steps. 

� The real parameters (white lines) can be measured by emtec devices. 

� By using the testing results the process parameters can be adjusted/optimized (green 

lines). 


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Use of emtec measurement devices for surface characterization of 

paper/board and for process optimization 

QA, process control: Fingerprint method – acquisition of process relevant parameters – 

preparation of a data base with comparison of PDA results of good/average/poor samples to 

determine the specifications and to assure compliance with the specifications. 

Trouble shooting, complaint management: Identification of reasons for malfunctions in 

the process, caused by surface pore structure/surface sizing problems 

Product/Process optimization, R&D: Extremely efficient tool to save considerably money, 

time, material, man power, etc. by avoidance of machine tests by performing of tests with 

high information level out of the machine in the lab, and by efficient process optimization 

Furthermore: the PDA.C 02 is designed as a Modular System. By using specific 

modules it is possible to simulate real converting processes like coating, gluing or 

printing. The measurements are performed under conditions (liquid contact with 

pressure impulse, high shear impulse) similar to the real process. 

How should the measurement devices be used? 

• Analysis of the manufacturing/converting process; description of the problem as 

exact as possible; evaluation of the converting process resp. end customer feedback; 

especially considering dynamics of processes 

• Determination: What to measure? Identification of the process relevant parameter to 

be measured (for paper/board these are usually surface porosity, surface 

hydrophoby) 

• Determination: How to measure? Specification of the measurement procedure (PDA 

configuration, test liquids, test conditions) 

• Evaluation of the measurement results, using the PDA standard measuring 

parameters t95/t99 and MAX, or assessment of the 

Dynamics of the 

process – which is the relevant value/curve area of the PDA 

measured curves (usually it is the short term area)? 

data base, determination of specifications 

• Preparation resp. completion of a 

• Evaluation of probable run-ability of a certain product within the process using the 

PDA measurement data 

The PDA system provides exactly the information that is 

needed for the process optimization, to predict the 

converting quality and to avoid complaints! 

The PDA Modular Measuring System makes your life 

easier! 


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PDA-Presentation (Glueability+Printability+Coating+Base+Paper)

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